Author: xmetman

I’ve never felt an earthquake before but I have now! At almost precisely 1430 UTC we felt the effects of a magnitude 4.9 earthquake down here in Devon. The epicentre of the earthquake itself was apparently in south Wales (fig 1). At the time I was sat in my office chair – programming as usual – when it started a series of wobbles to-and-fro – very unusual!

It’s turning out to be quite a wet February 2018 more especially in western areas. The wettest place in the SYNOP observations is Capel Curig as usual with 6.55″ of rain up until this morning (fig 1). There are still some drier spots around though, notably in eastern Ireland, the Vale of York and the southeast of Scotland, although I only have a 79% record for Edinburgh Gogarbank.

The latest run of the GFS has come back into line with the ECMWF model in establishing a cold anticyclonic easterly across the country by T+144. After that the GFS enters the twilight zone by introducing a number of cyclonic outbreaks that get embedded in the cold easterly flow, these suggest a high chance of substantial spells of snow especially in eastern districts by the end of the month (fig 1).

Figure 1 – Courtesy of www.wxcharts.eu

Even the Met Office are now warning of the increased chances of this happening thanks to the recent Sudden Stratospheric Warming event above the North Pole. Professor Adam Scaife, of the Met Office Hadley Centre, said:

“Signs of this event appeared in forecasts from late January and in the last few days we have seen a dramatic rise in air temperature, known as a Sudden Stratospheric Warming, at around 30 km above the North Pole. This warming results from a breakdown of the usual high-altitude westerly winds and it often leads to a switch in our weather: with cold easterly conditions more likely to dominate subsequent UK weather.”

Frank Saunders the Met Office Chief Operational Meteorologist said

“A Sudden Stratospheric Warming implies around a 70 per cent chance of cold conditions across the UK. There tends to be a lag of about 10 days before we see the downstream effects on the UK’s weather, as it takes time for the influence in the upper atmosphere to feed down to those levels where our weather happens. The outcome for the UK’s weather is still uncertain, but forecasts from computer models at the Met Office and at other centres are beginning to coalesce around a greater likelihood of cold conditions in the days and weeks to come.”

Just when we thought that we finally might see some winter down here in the south it now looks like two of the three main NWP models can’t agree with how things will work out in just 6 days time. The difference at T+144 between the GFS and the ECMWF models is massive, with the GFS going for a cyclonic SW’ly (fig 1), and the ECMWF for an anticyclonic E’ly (fig 2). All I can think is that it must be how each model handles the current SSW that is behind these two widely different solutions.

It looks very like the 2017/18 Arctic sea ice maximum will beat the record low set only last year. At the moment (14th Feb) the anomaly stands at just 90.4% of the average for this day of the year, that’s 2.3% lower than it was this time last year, and equates to a massive 352,000 square kilometre less of sea ice (fig 1).

The fact that we are now in the grips of a SSW event doesn’t bode well for a late surge in sea ice as we approach the time of maximum in the Arctic. The mean date for the maximum is the 8th of March, and although unlikely, the maximum may have already occurred! The maximum so far this season occurred over a week ago now on the 5th (13.979 million square kilometres) which would make it extremely early, because the earliest maxima on record in the last 40 years occurred on the 21st of February in the years 1987, 1994 and 1996 (fig 2).

There is no doubt that a change of type will occur in the next week or two because of the SSW that started late last week. The next problem is where the actual block will be positioned and orientated. The two main available NWP models at T+240 have different views on that matter at the present time. The ECMWF has the block centred over the southern North Sea at the 500 hPa level and aligned northeast-southwest (fig 1), whilst the GFS has it centred over NE Greenland, and ridging more or less north-south across Iceland towards western Ireland (fig 2).

Figure 2 – Courtesy of www.wxcharts.eu

The exact position of where any block sits at the 500 hPa level, will make a big difference at the surface, because it dictates the surface flow and the source of the coldest air. As you can see the ECMWF at T+240 has higher than average 850 hPa temperatures across the UK in a strong SE’ly flow, and the coldest air over SE Europe and the Balkans (fig 3).

Figure 3 – Courtesy of www.wxcharts.eu

Meanwhile the GFS model has the coldest air at 850 hPa over Scandinavia with the UK in a much colder regime and the flow more easterly and not as strong (fig 4).

Figure 4 – Courtesy of www.wxcharts.eu

Here’s what the experts are saying down at the Met Office about the medium term (fig 5).

The Global Forecast System has been nominated for a Hugo award for its latest model run for the UK (fig 1)! The Hugo Awards are a set of literary prizes that are given annually for the best work of science fiction or fantasy. This is the first time that a piece of software has ever been nominated, but the trilogy of T+288, T+312, & T+336 forecast charts do meet the essential criteria for any nomination, in that they are both science and fiction.

Figure 1 – Courtesy of www.wxcharts.eu

Despite this tongue in cheek humour, and as a snow lover, I would love something like this to happen, and perhaps now that the polar vortex is split we will finally see a change in type that means something like is possible and not just science fiction.